The present invention relates to a router base table insert. In the prior art, devices designed to be used to support a rotary tool in an adjustable manner are known. U.S. Pat. Nos. 2,799,305 to Groehn, 2,888,965 to Phillips, 3,581,787 to Bane and 4,484,608 to Ferdinand et al. are known to Applicant. However, none of these patents includes all of the various aspects and features of the present invention, especially concerning the vertical adjustability of an inverted router as well as the particular manner of support of the inverted router under a table, which features are included in the present invention.